A new enzymatic indirect-sandwich immunoassay for carcinoembryonic antigen has been developed in this laboratory. The specific objectives for the year of research support requested are as follows: 1) To apply the new enzymatic indirect-sandwich immunoassay for CEA to the range between 2.5 and 40 ng of CEA per ml plasma. 2) To increase sensitivity of the new assay for CEA, eventually enabling the examination of the relationship between fluctuations in CEA level in the 0.01 to 2.5 ng/ml of plasma range in serial measurements and the patient's clinical status. 3) The new assay is presently performed in a total of 3-1/2 laboratory working days. Conditions will be sought to decrease the length of time required for the assay. 4) Studies will be initiated on the detection of possible anti-CEA antibodies in human plasma by appropriate adaptation and modification of enzymatic indirect-sandwich immunoassay for CEA. The new enzymatic immunoassay for CEA may be performed by clinical and hospital laboratories not equipped for use of radioisotopes. Use of this assay should permit greatly enlarged screening programs for CEA and anti-CEA. With enlarged screening programs, the relationships between CEA and colon cancer will be more clearly understood.